Method for the continuous manufacture of battery electrodes - Patents.com

Abstract

The present invention relates to a method for the continuous manufacture of battery electrodes from an electrode powder mixture comprising an active material, a binder material and a conductive additive. First, the manufacture of a powder mixture is carried out by adding an active material, a binder material and a conductive additive. This is followed by a powder pretreatment of the powder mixture consisting of the active material, the binder material and the conductive additive in a mixer, during which powder pretreatment, powder mixing and powder homogenization and binder fibrillation are carried out. Then, a continuous impact concentration grinding of the powder mixture is carried out, which results in a powdery and flowable electrode powder mixture. Then, a step is carried out of transferring the produced powdery and flowable electrode powder mixture by means of an outlet opening, by spilling and / or pouring, into a calendar gap with a desired width and thickness. There, a step is carried out of the electrode powder mixture present in the calendar gap by shear forces inside the calendar gap to produce a film. This film is then transferred onto a current collector foil, compressed into a film with a desired target thickness and processed into a battery electrode.

Description

[Technical field]

[0001] The present invention relates to a method for continuously producing battery electrodes from an electrode powder mixture that includes an active material, a binder material, and a conductive additive.

[0002] A battery is an electrochemical-based storage for electrical energy. An accumulator is a rechargeable battery. Batteries are an important component, especially for the future of battery electric vehicles. Batteries are distinguished by high energy density and specific energy, high cell voltage, extremely long storage capacity with low self-discharge, and a wide temperature range for storage and operation. Due to their high energy density, batteries therefore play an important role in achieving long driving ranges for electric vehicles.

[0003] A battery has two electrodes, between which an electrolyte containing freely movable charge carriers is located, and which are insulated from each other by a separator, which is a porous membrane. Lithium-ion batteries, for example, work by individual lithium ions moving between the electrodes during discharge and charging and being stored in the active materials of the electrodes. During discharge, lithium leaves the negative electrode, which usually contains copper as a conductor, and electrons are released at the same time. The active material of the positive electrode of a lithium-ion battery, for example, contains mixed oxides, and in the positive electrode, graphite or amorphous carbon compounds are often used. Lithium is stored in these materials. During discharge, lithium ions move from the negatively charged electrode through the electrolyte and the separator to the positively charged electrode. At the same time, electrons, as carriers of electricity, flow from the negatively charged electrode through an external electrical connection (for example a cable connection) to the positively charged electrode, which usually contains aluminum as a conductor. During charging, the process is reversed. In this case, lithium ions migrate from the positively charged electrode through the electrolyte and separator to the negatively charged electrode. Cell geometries of individual cell materials include cylindrical, prismatic and stacked cell geometries, among others. Depending on the application, one battery cell or multiple cells are used. In the case of multiple cells, these cells are connected in series in a module. In this case, the required capacity determines whether multiple battery cells are connected in parallel or not. The connected modules form a battery system.

[0004] In battery production, in particular, various criteria must be taken into account and manufacturing tolerances must be taken into account. This applies, for example, to coating defects. That is to say, in particular, the production of the electrodes and the recipes and processes used therein are of special importance. During electrode production, the active material is usually mixed with binder material and conductive additives and deposited on a metallic conductive foil. The conductive additives improve and ensure the electronic conduction between the active material particles, which are mostly only averagely or poorly conductive. Even when graphite, which is actually a good conductor, is used as the storage material, the addition of conductive additives to the anode cannot be omitted. The binder material is an electrochemically inert material whose role is to stabilize the mixture of the active material and the conductive additives and to form the contact with the collector. Therefore, with as small an amount of binder material as possible, a sufficiently uniform distribution of the binder material should be achieved in order to ensure a good adhesion of the electrode layer to itself and to the collector on a lasting basis. The conductivity must be uniform in the three-dimensional structure of the electrode layer and especially pronounced towards the collector. Typically, known methods for producing electrodes involve mixing and dispersion of the starting materials, during which a suspension (slurry) or paste is formed. After dispersion, depending on the method, a suspension or a highly viscous paste results. This is then cast into a film on a collector, which is then dried. The film is then cut and rolled on the collector.

[0005] US 2014 / 0210129 describes a method for manufacturing a carbon electrode material capacitor. The method includes mixing materials in a twin-screw extrusion apparatus, where the mixed material includes a substantially non-fibrillated binder and a carbon material. Thereafter, extrusion of the mixed material occurs through a nozzle of the twin-screw extrusion apparatus.

[0006] US Patent No. 5,566,888 describes a method and an apparatus for recycling resin components. In this case, the coated or clad resin component is coarsely ground. The coarsely ground resin component is heated and extruded to produce an extruded strand or an extruded foil. The extruded body is rolled and stretched. The wound foil is pulverized and separated into the base resin component and the coated film or stack component.

[0007] US Patent No. 6,284,192 describes a method for extruding zinc or nickel electrode materials. For this purpose, a homogeneous batch is mixed from raw materials consisting of a zinc or nickel source and further containing substantially non-fibrillated polytetrafluoroethylene (PTFE) as an additive. The batch is conveyed into an extrusion device where it is extruded through a forming element.

[0008] In electrode production, most of the energy required for drying and solvent recovery in wet coating is omitted. In this case, the main challenge is to produce thin and uniform electrode layers at high process speeds at the same time. The use of pastes or suspensions (slurries) creates the additional challenge that these are applied, for example, as extrudates from nozzles or similar flow-technical components onto foils or rolls. The extrudates therefore have such large layer thicknesses that multiple rolling steps are necessary to obtain the target thickness for the film due to the limited selectability of the nozzle openings, which must not fall below a certain size. This requires larger equipment with multiple process stages and there is a larger material load. Furthermore, it is difficult to maintain the manufacturing tolerances.

[0009] The problem underlying the present invention is therefore to at least partially overcome the above-mentioned disadvantages of the prior art and to provide a method which allows the continuous production of battery electrodes for solvent-free electrode production.

[0010] This problem is solved by a method with the features of the independent claims. Advantageous configurations of the invention are defined in the dependent claims.

[0011] According to the invention, a method for the continuous production of battery electrodes from an electrode powder mixture comprising active material, binder material and conductive additive is provided. In this case, first, the production of the powder mixture is carried out by adding the active material, binder material and conductive additive. This is followed by a powder pretreatment of the powder mixture of active material, binder material and conductive additive in a continuous mixer, during which powder pretreatment, powder mixing and powder homogenization and binder fibrillation take place. Then, a continuous impact intensive grinding of the powder mixture is carried out, which results in a powdery and flowable electrode powder mixture. In other words, the occurrence of a wet or water-containing mixture similar to a paste or suspension (slurry) is prevented. The powdery and flowable electrode powder mixture thus produced is then transported by an outlet opening into the calender gap in the desired width and thickness by spilling and / or pouring without the use of flow mechanical components. Due to the consistency of the substantially dry flowable electrode powder mixture, the transport can be carried out according to the invention without the use of nozzles or similar components. In other words, the electrode powder mixture can be removed by flowing, pouring or dropping (downward) as a powdered, flowable electrode powder mixture, rather than being extruded by pressure through a nozzle or the like in the form of an extruded strand. A film is then produced from the electrode powder mixture present in the calendar gap by shear forces inside the calendar gap. The film is then transferred onto a current collector foil in a rolling device, and the film on the current collector foil is compressed into a battery electrode having a desired target thickness.

[0012] In particular, no solvent is added to the electrode powder mixture (including the active material, the binder material, and the conductive additive). In other words, the method is carried out substantially without the use of solvent. This does not exclude that the aforementioned contents may contain unavoidable residues or traces of solvent to the extent that a flowable consistency is maintained. In particular, the total content of solvent in the electrode powder mixture is less than 0.2% by weight, preferably at most 0.1% by weight.

[0013] Optionally, the film can be calendered in another calender stage before it is transferred to the current collector foil.

[0014] Usually, according to the prior art, nozzles are used in extrusion devices. Nozzles are technical devices that influence the fluid when it passes from the pipe flow into the free space, in which case the nozzle forms the end of the pipe. The nozzles are usually tapered along their entire length and, in the context of the prior art electrode production, have a special shape at the outlet for shaping the extruded strand.

[0015] It should be noted that the active material, binder material and conductive additive may each be a mixture of multiple components.

[0016] Fibrillation means that the binder material, e.g. PTFE, initially present in particulate form, is pulled into "threads" or "fibers". This is done by friction and shear of the particulate binder material. Such a fibrous structure is necessary to guarantee the mechanical quality of the product. Conventional electrodes have a PVDF binder that dissolves and distributes in the form of smaller and finer globules, binding the materials together. The preferred PTFE binder, which is stretched into nanofibers, provides mechanical stability between the remaining particles purely by physical force action.

[0017] In the following, in the context of the present invention, batteries should be considered to also include accumulators.

[0018] During powder pretreatment, the components, including active material, binder material and conductive additive in defined proportions, are inter alia mixed according to the production method. The mixture is then thoroughly homogenized. Further dispersion is performed to ensure homogenous distribution of the active particles, binder material and conductive additive. Energy input into the powder mixture is then performed. Each method, or each successive mixer used for each method, has its own characteristics regarding the energy input and homogenizing action for each powder mixture. When scaling up the process, the specific energy input per volume fraction is an important parameter.

[0019] According to the method of the invention, the transfer of the powdery and flowable electrode powder mixture is preceded by a continuous impact-intensive grinding of the powder mixture. In order to ensure sufficient grinding of the produced powder mixture (flowability and further processing into a uniform layer), an increased impact-intensive load is required. In this case, the coupling of powder pretreatment with continuous impact-intensive grinding is advantageous. The impact load required for grinding the powder mixture obtained by powder pretreatment is thereby increased by being complemented by a second subsequent process for ensuring the grinding action. This allows the size of the electrode powder particles to be further reduced and in particular the agglomerates formed during the bond fibrillation, which may be present, to be deagglomerated. This allows the solvent to be dispensed with and at the same time the flowability to be improved.

[0020] The further grinding by the impact intensive grinding process is preferably carried out by ultracentrifugal mill or counter jet mill or impact mill. Particularly preferably, a classifier mill is used for the further grinding. Classifier mills are preferred because they provide a less intensive method, therefore the material is not damaged, it is easier to monitor and control, and they have a particularly lower process cost than comparable equipment.Furthermore, it is important that during this further grinding step, reliable deagglomeration is carried out, which can be carried out appropriately by classifier mills.

[0021] The method of the invention allows the continuous production of battery electrodes for solvent-free electrode production, where a high degree of fibrillation is achieved without excessive mechanical stress on the material, unlike previously known solutions. This avoids the additional energy input involved in drying, since drying is not necessary. Furthermore, rolling steps that may be subsequently linked to electrode production can be reduced, which reduces process costs and improves material protection of the equipment and of the resulting film. Scaling up is also more easily achieved by powder mixing and powder homogenization and binder fibrillation in one continuous process step, instead of multiple batch processes that can only be scaled up for large production partially by numbering up.

[0022] In this case, the addition of the components can take place in a continuous mixer in which the powder pretreatment is carried out, where the addition of the components can take place in different loading areas or jointly in one local loading area.

[0023] Optionally, during powder pretreatment, milling is also performed after powder mixing and powder homogenization, and binder fibrillation, to improve flowability.

[0024] In a preferred configuration of the invention, the continuous mixer is a twin-screw extruder or a continuous kneader, and it is envisaged that the powder mixing and homogenization, the binder fibrillation and the optional grinding during the powder pretreatment are combined in the twin-screw extruder or the continuous kneader. According to the invention, this is a continuous process. This continuous process comprises the steps of powder mixing and homogenization, the binder fibrillation and the optional grinding. These three steps are carried out in one continuous mixer. Preferably, this mixer is a twin-screw extruder or a continuous kneader. The use of a twin-screw extruder is an advantageous process variant for powder pretreatment, since the twin-screw extruder allows as much flexibility as possible for the individual zones along the screw. In the zones, activation by shear and possibly by slightly elevated temperature takes place, which allows optimal binder fibrillation.

[0025] According to an advantageous configuration of the invention, in the continuous powder pretreatment by the mixer, a first zone and / or a second zone and / or a third zone are present. In this case, the first zone is designed to have a significant mixing and grinding action for homogenization, the second zone is designed to have a high kneading and shearing action for binder fibrillation, and the third zone is designed to have a relatively less significant grinding action in order to produce a flowable and non-dusty powder. The structure of the continuous mixer therefore has various zones. Inside the mixer, the powder mixture is subjected to a successive treatment, including powder mixing, powder homogenization, binder fibrillation and grinding. These steps therefore have different roles that should be performed on the powder mixture. The first zone should therefore have a significant mixing action in comparison with the second and third zones in order to ensure a homogenous powder mix. In this case, a pronounced mixing action in the first zone is particularly important, since it is more difficult to achieve a homogeneous mixture in the dry form compared to the "wet" process, which involves a solvent and in which a slurry, suspension or paste is present. In contrast, the role of the second zone is to sufficiently fibrillate the binder material. Usually, in the prior art methods, the binder material is dissolved in a solvent. This can be done before the addition to the mixer or in the mixer. During the subsequent drying, the binder material is located between the individual particles and exerts its binding action. However, in this case, this should be avoided according to the method of the invention, since the solvent for dissolution should be omitted for the reasons mentioned above. Therefore, since the fibrillation must be achieved mechanically assisted without the use of a solvent, a corresponding second zone is preferably provided in the mixer. After the powder mixing and powder homogenization and the binder fibrillation, the components of the powder must be further ground to provide a flowable powder. This can be promoted by optional grinding during the powder pretreatment. In particular, when this comminution is performed, a third zone is provided, which should be characterized by a stronger comminuting action compared to the second zone.The first zone, the second zone and the third zone are arranged in the order listed along the conveying direction.The first zone can be formed for this purpose, for example, by the screw of the extrusion device, in which case the screw of the first zone has a gear wheel forming a grinding mechanism.The second zone can have, for example, a kneading mechanism that includes trapezoidal elements.The third zone can again have a gear wheel, in which case fewer gear wheels are used than in the first zone.

[0026] Preferably, the conductive additive is added only after the powder mixing of the active material and the binder material. This makes it possible to avoid that the conductive additive wets the binder, which would prevent it from being able to be deagglomerated and fibrillated any further. Alternatively, in order to ensure the best possible bonding, preferably only the active material and the conductive additive are mixed together first. In this case, the binder material is added only afterwards to the mixture of the active material and the conductive additive.

[0027] In a preferred configuration of the invention, it is envisaged that the total amount of binder material is preferably in the range of 0.2-2% by weight of the total amount of the electrode powder mixture, in particular in the range of 0.4-1.6% by weight, preferably in the range of 0.5-1.2% by weight, particularly preferably 0.75% by weight. An electrode powder mixture is provided which does not need to be dried following its manufacturing method. The entire binder material is activated so that the powder mixture remains in a powdery and flowable state throughout. The binder material is furthermore an inactive material. Thus, the binder material is not essential for the operating mode of the battery. On the contrary, the binder material adversely affects the operating mode of the battery, since due to its presence it occupies a certain percentage of the total mass and volume, which is undesirable. Furthermore, the binder material is electrically insulating, thereby impairing the electrical conductivity and accessibility of the active material. Thus, a low binder proportion prevents a high proportion of inactive material in the form of binder, which has an advantageous effect on the operation of the battery subsequently produced from such an electrode powder mixture.

[0028] Advantageously, it may be envisaged that the battery electrode is a cathode (positive electrode) and the total amount of active material is at least 95% by weight of the total amount of the powder mixture and comprises a mixed oxide of lithium and at least one metal selected from Ni, Co, Mn, Al. This provides an electrode powder mixture with a high percentage of active material. Due to the method of the invention and the optimized binder fibrillation, and at the same time the absence of solvents, such a cathode has a higher mechanical stability and excellent chemical properties. The absence of solvents eliminates the drying step and improves the equipment footprint.

[0029] Advantageously, the battery electrode is an anode (negative electrode) and the total amount of active material is at least 95% by weight of the total amount of the powder mixture, and is preferably graphite and / or SiO x It may be envisaged that the anode may comprise a binder fibrillation agent, which provides an electrode powder mixture with a high percentage of active material. Due to the method of the invention and the optimized binder fibrillation, and at the same time the absence of solvents, such an anode has higher mechanical stability and superior chemical properties. The absence of solvents eliminates the drying step, improving the equipment footprint.

[0030] Preferably, the percentile value D90 of the particle size distribution of the electrode mixture is less than 500 μm. With such a particle size distribution, the flowability of the powdery, flowable electrode powder mixture is improved, so that further processing can be easier and more accurate. A percentile value D90 of less than 500 μm means that 90% of the electrode powder mixture is less than a maximum of 500 μm.

[0031] In an advantageous configuration, prior to the powder pretreatment of the powder mixture, the homogenization of the active material and the binder material and optionally the conductive additive is carried out in a separate process, preferably by comminution of the corresponding mixture, in particular by means of an ultracentrifugal mill.

[0032] According to a further advantageous configuration of the method, it is provided that the battery electrode is an electrode of a lithium-ion battery electrode, in which case it is particularly important to use a small proportion of binder and to ensure good distribution of the conductive additive.

[0033] When producing a cathode, PTFE is used as a binder, particularly preferably PTFE with a primary particle size greater than 1 μm.In this case, particularly preferred conductive additives are conductive graphite and carbon black, CNT and similar materials.The proportion of conductive additive is preferably less than 4% by weight.

[0034] When producing the anode, a mixture of PTFE and PVDF is preferably used as binder. Preferably, the proportion of PVDF is reduced and instead a binder material is used which is electrochemically stable to the high negative potential of the anode, in particular PEO (polyethylene oxide) is used in this case. Particularly suitable conductive additives correspond to the conductive additives of the electrode powder mixture production for the cathode. The proportion of conductive additive is preferably less than 4% by weight.

[0035] The invention further relates to a method for producing battery electrodes, in which the produced powdery, flowable electrode powder mixture is transferred by outflow and / or pouring through an outlet opening into the assembly device and / or into the calender gap of the calender, i.e. into the gap between two counter-rotating rolls. In other words, the flowable powder is fed directly from the outlet of the continuous mixer to the calender. The processes may also be connected to one another, for example, via vacuum transport. In the sense of the invention, "direct supply" means that the powder is not provided from the calender to the subsequent process stage via a nozzle or the like, but in the form of outflow and / or pouring from the outlet of the continuous mixer. An intermediate transport between the continuous mixer and the calender may therefore also take place, in which case the supply to the intermediately connected transport process takes place in the form of this direct supply, which continues to the calender. If the displacement of the continuous mixer is dimensioned accordingly, several calenders can also be connected. This step is followed by a step of forming the electrode powder mixture in the calender as a film supported on a roll. This is achieved by varying the rotation speed of the rolls.Then, the film supported by the roll is transferred onto the current collector foil in the middle calendar gap, and the film supported by the roll on the current collector foil is compressed into a battery electrode having the desired target thickness in the middle calendar gap or another calendar gap.The electrode powder mixture produced during the method is then used for corresponding further processing to form a battery electrode by coating on the current collector foil with the desired criteria and requirements described at the beginning.

[0036] Optionally, varying the rotation speed of the rolls results in forming a roll-supported film, which is passed through further calender stages where it is rolled before being transferred onto the current collector foil.

[0037] The calender is preferably a multi-stage calender, in particular a four-roll calender. According to the methods known from the prior art, a paste or suspension (slurry) is produced in the mixer. The paste or suspension is a mixture of relatively dense solid substances suspended in a liquid. The paste or suspension flows out of the mixer, which is usually a twin-screw extruder, by means of a nozzle. In a subsequent step, a film is formed from this extruded strand by rolling, the width of the film being produced by this rolling. According to the invention, a flowable electrode powder mixture is produced according to the invention in a continuous mixer. In a subsequent step, the flowable electrode powder mixture is applied to the rolls of the calender. In this case, the desired width of the future film can already be defined by pouring out and / or pouring out. For this purpose, the flowable electrode powder mixture can be poured out on the rolls with the corresponding width. The use of a nozzle can thus be dispensed with. This makes it possible, inter alia, to prevent the occurrence of disadvantageous counterpressure due to the narrow opening of the nozzle. Such counter pressure is often attempted to be limited by a correspondingly large nozzle opening, which results in a correspondingly large extrusion strand. The nozzle shape itself can certainly be formed with various geometries at its outlet, but they all have in common that the cross section of the nozzle outlet surface is reduced compared to its inlet, which leads to an increase in pressure. When subsequent rolling is performed, the presence of a minimum nozzle opening increases the number of rolling steps to reach the target thickness by repeatedly rolling the extrusion strand, which also results in additional material loads. The rolling steps also result in wear of the equipment, for example. Furthermore, the costs of such components, such as the nozzle, can be eliminated, and the maintenance of these components is no longer necessary. Furthermore, the nozzle results in high shear forces, which can also change the material in an undesirable way. Furthermore, the flowable electrode powder mixture allows a large degree of freedom in determining the geometry of the film, especially with regard to the layer thickness.

[0038] Particularly preferably, the calender has four rolls.

[0039] According to a further configuration of the method according to the invention, it is envisaged that the resulting powdery and flowable electrode powder mixture is transferred by overflow and / or pouring through an outlet opening into the assembly device and / or into the calendar gap of the calendar, i.e. into the gap between two counter-rotating rolls. This is followed by a step of forming the electrode powder mixture into a free-standing film in the calendar. For this purpose, the rolls of the calendar rotate at the same rolling speed. Furthermore, rolling of the free-standing film is carried out in another calendar stage in order to reduce the film thickness and increase the film density. This free-standing film is then transferred onto a current collector foil and compressed in a rolling device into a battery electrode with the desired target thickness.

[0040] Optionally, the same rotational speed of the rolls results in forming into a free-standing film, which, supported by the rolls, is passed through further calender stages where it is rolled before being transferred onto the current collector foil.

[0041] Further advantageous configurations of the invention are obtained with the further features set out in the dependent claims.

[0042] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless specifically stated otherwise.

[0043] The present invention will now be described in the following by way of example with reference to the accompanying drawings. [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 is a diagram showing a schematic structure of a battery. [Diagram 2] FIG. 1 illustrates a combined apparatus and process diagram for manufacturing a battery electrode according to an aspect of the present invention, including a twin-screw extrusion apparatus. [Diagram 3] 4 is a flow chart illustrating a method for manufacturing a battery electrode according to a first aspect of the present invention. [Figure 4]5 is a flow chart illustrating a method for manufacturing a battery electrode according to a second configuration of the present invention.

[0045] 1 shows a battery 10 with two electrodes 11, 12 between which an electrolyte 13 containing freely movable charge carriers is located and which are insulated from each other by a porous membrane separator 14. Electrode 11 is the cathode of the battery and has a cathode conductor 111 and a cathode active layer 112 arranged on the conductor 111. Electrode 12 is the anode of the battery and has an anode conductor 121 and an anode active layer 122 arranged on the conductor 121. In the following, the cathode and anode conductors 111, 121 are referred to as current collectors 111, 121, since they are made from current collector foils coated with an electrode powder mixture.

[0046] 2 illustrates in a combined apparatus and process diagram a method for manufacturing battery electrodes according to an aspect of the present invention, including a twin-screw extrusion apparatus 20. The diagram focuses on the twin-screw extrusion apparatus 20 and its incorporation into the context of the method according to the present invention and further (but not all) method steps, providing a good understanding of the operation of the twin-screw extrusion apparatus 20 in combination with the further method steps.

[0047] The twin-screw extrusion device 20 comprises a drive unit 21 which drives the screws arranged in the screw region 22 and thus mixes and conveys the powder mixture. The screws extend longitudinally along the screw region 22 and engage with one another. Furthermore, the screws are rotated in opposite directions by a drive. Furthermore, the twin-screw extrusion device 20 has an outlet opening 23 which allows the produced electrode powder mixture to be transported for a subsequent step. The transport is effected by the outlet opening 23, by the outflow and / or pouring or dropping of the electrode powder mixture from the outlet opening 23.

[0048] The conveying direction of the twin-screw extrusion device 20 runs from the drive 21 in the direction of the discharge opening 23. Furthermore, the screw region 22 comprises a powder filling region 24 and an optional conductive additive filling region 25 or alternatively a binder material filling region 25 arranged downstream of the powder filling region 24 in the conveying direction. Optional in this context does not mean that the addition of the conductive additive or alternatively the binder material is omitted, but rather that the addition of the conductive additive or alternatively the binder material can take place later than the addition of the active material and the binder material or the corresponding conductive additive. Alternatively, a simultaneous addition of the active material and the binder material or the conductive additive takes place, rather than a later addition. This is evident from the method steps S1 and S13 associated with the respective filling regions 24, 25.

[0049] The material to be processed is fed into the screws of the twin-screw extrusion device 20, for example, via a funnel located in the upper screw cylinder (not shown). Furthermore, the screw region 22 according to a preferred embodiment of the invention comprises a first zone I, a second zone II and a third zone III. The first zone I is designed with a significant mixing and grinding effect for homogenization, the second zone II with a high kneading and shearing effect for binder fibrillation, and the third zone III with a relatively less significant grinding effect for the production of a flowable and non-dusty powder. The screws therefore have a target-specific screw design in each region.

[0050] Inside the twin-screw extrusion device 20 the powder mixture is subjected in the conveying direction to successive treatments including powder mixing, powder homogenization, binder fibrillation and optional comminution, with the individual steps being carried out in the conveying direction in the sequence of steps used before them. Of course, these zones cannot be entirely limited to one action, but it is particularly desirable to focus on one step each inside the screw region 22. Between the first zone I and the second zone II and between the second zone II and the third zone III, return conveying elements are arranged.

[0051] In the first zone I, a grinding mechanism is formed, for example, by a screw with intermeshing gears, which develops a mixing and grinding action. In contrast, the second zone II contains a kneading mechanism, which can be formed by trapezoidal elements. In this case, the grinding action is therefore reduced, but the fibrillation action is improved. The third zone III also contains a grinding mechanism, where the number of intermeshing gears is less than in the grinding mechanism of the first zone I. The grinding action here is therefore reduced.

[0052] During the method for manufacturing a battery electrode described below, the active material, binder material, and conductive additives are processed into a powder mixture after addition to the first zone I by the screw, and the coarser components are ground by a grinding mechanism in the first zone I.

[0053] The powder mixture is conveyed by the screw in the conveying direction to the second zone II, where the relatively coarse / granular components are returned by the return conveying element and passed to the second zone II only when they have a suitable particle size similar to the other powder mixture exiting from the first zone I. In the second zone II, the powder mixture is kneaded by the screw, which includes a kneading mechanism, where the binder material is fibrillated. When the binder material is fibrillated, a powder mixture is obtained in the second zone II, which includes the binder material mixed therein and which includes the comminuted active material and the conductive additive, which are crosslinked with the fibrillated binder material.

[0054] The powder mixture is conveyed by the screw from the second zone II to the third zone III in the conveying direction. In the optional third zone III, the fibrillated binder material is then further comminuted by a comminuter mechanism arranged therein. The finished electrode powder mixture is then produced, which is conveyed by the screw from the discharge opening 23 and thus discharged therefrom.

[0055] A method for producing a battery electrode according to a first configuration of the invention is now described with reference to Fig. 3. In this case, a twin-screw extrusion device 20 of the construction shown in Fig. 2 is preferably part of the method. Fig. 3 shows in this case a flow chart of the method for producing the electrodes. It should be noted that in this case, the electrode preparation for one of the two electrodes 11, 12 is produced according to the method according to the invention, or both are produced, but in this case the starting materials are different.

[0056] The method starts with step S1. This step includes the addition of a powder mixture of active material, binder material and conductive additive. In this case, first the production of the powder mixture takes place via the powder filling area 24 by the addition of the active material in step S11, the addition of the binder material in step S12 and the addition of the conductive additive in step S13. The addition of the individual components in step S1 can be carried out by individual steps S11, S12 and S13 together or optionally for each component. The addition of the conductive additive in step S13 can, in this example, optionally only take place after the powder mixing of the active material and the binder material by steps S11 and S12. The addition in step S1 is carried out in the first zone I, and in the case of a later addition of the conductive additive in step S13, this step takes place downstream, but also in the conductive additive filling area 25, which is still in the first zone I.

[0057] This is followed in step S2 by powder pre-treatment of the powder mixture of active material, binder material and optionally subsequently added conductive additives, during which powder mixing and powder homogenization, binder fibrillation and optional grinding take place during powder pre-treatment in step S2. The mode of operation of the different zones of the twin-screw extrusion device 20 has already been explained herein with reference to FIG.

[0058] In step S3, further processing of the electrode powder mixture removed from the twin-screw extrusion apparatus 20 takes place. In order to ensure sufficient comminution of the produced granulation (flowability and further processing into a uniform layer), an impact-focused load is applied in this case. The continuous process for powder pretreatment by the twin-screw extrusion apparatus 20 is coupled to a continuous impact-focused comminution process. This step S3 can be carried out, for example, by means of an ultracentrifugal mill, an opposed jet mill or, in particular, a classifier mill.

[0059] The resulting powdery and flowable electrode powder mixture, following the powder pretreatment and the continuous impact concentration grinding, is then transferred by the discharge opening 23 into the collection device and / or the calender gap of the calender, i.e. the gap between two counter-rotating rolls, by overflow and / or pouring. In other words, the electrode powder mixture can be discharged by overflow, pouring or dropping (downwards) as a powdery and flowable electrode powder mixture, rather than being extruded by pressure in the form of an extruded strand by a nozzle or the like. Optionally, surplus electrode powder mixture can be stored inside a silo, not shown in detail, by the calender in the form of intermediate storage in step S4, before further processing on the current collector foil.

[0060] In step S5, the electrode powder mixture is further processed into a roll-supported or free-standing film. For this, a roll-supported or free-standing film is produced from the electrode powder mixture present in the calendar gap by shear forces inside the calendar gap. The film is then transferred onto the current collector foil 111, 121 in the middle calendar gap, and this film on the current collector foil is compressed in a rolling device into a battery electrode 11, 12 with a desired target thickness.

[0061] Figure 4 shows a flow chart of a method for manufacturing battery electrodes 11, 12 according to a second configuration of the invention. In this case, the method differs from the method described with reference to Figure 3 in that the active material and the binder material, or possibly the conductive additive, are homogenized in a separate process before being fed to the continuous powder pretreatment in step S2. This can be done, for example, by ultracentrifugal milling in step S1'. The other method steps do not differ from the method described with reference to Figure 3. [Explanation of symbols]

[0062] 10 Battery 11 Cathode 111 Cathode current collector 112 Cathode active layer 12 Anode 121 Anode current collector 122 Anode active layer 13 Electrolytes 14 Separator 20 Twin screw extrusion equipment 21 Drive unit 22 Screw Area 23 Extraction opening 24 Powder filling area 25 Optional conductive additive filled area / Optional binder material filled area I First Zone II Second Zone III. The Third Zone

Claims

1. A method for continuously manufacturing battery electrodes from an electrode powder mixture including an active material, a binder material, and a conductive additive, comprising the steps of: - preparing a powder mixture by adding said active material, said binder material and said conductive additive, - powder pre-processing the powder mixture of the active material, the binder material and the conductive additive in a continuous mixer, during which powder mixing and powder homogenization and binder fibrillation are carried out; - Continuously impact crushing the powder mixture to obtain a powdery and flowable electrode powder mixture; - transporting the produced powdery and flowable electrode powder mixture into the calender gap by overflow and / or pouring, by means of an outlet opening, in the desired width and thickness, - producing a film from the electrode powder mixture present in the calender gap by shear forces inside the calender gap; - transferring the film onto a current collector foil in a rolling device and compressing the film on the current collector foil in the rolling device into a battery electrode having a desired target thickness; The method includes:

2. 2. The method according to claim 1, wherein the continuous impact intensive grinding is carried out by means of an ultracentrifugal mill or an opposed jet mill or an impact mill, in particular by means of a classifier mill.

3. 3. The method according to claim 1 or 2, wherein the continuous mixer is a twin-screw extruder or a continuous kneader, and the powder mixing and powder homogenization and binder fibrillation are combined in the twin-screw extruder or the continuous kneader.

4. 4. The method according to claim 1, wherein within the continuous powder pre-treatment there are a first zone and / or a second zone and / or a third zone, the first zone being designed to have a pronounced mixing and grinding action for the homogenization, the second zone being designed to have a high kneading and shearing action for the binder fibrillation, and the third zone being designed to have a moderately pronounced grinding action in order to produce a flowable and non-dusty powder.

5. 5. The method according to claim 1 , wherein the conductive additive is added only after powder mixing of the active material and the binder material, or the binder material is added only after powder mixing of the active material and the conductive additive.

6. The method according to any one of claims 1 to 5, wherein the total amount of binder material is preferably in the range of 0.2 to 2 wt.-% of the total amount of the powder mixture, in particular in the range of 0.4 to 1.6 wt.-%, preferably in the range of 0.5 to 1.2 wt.-%, particularly preferably 0.75 wt.-%.

7. 7. The method of claim 1, wherein the battery electrode is a cathode (positive electrode) and the total amount of active material is at least 95% by weight of the total amount of the electrode powder mix and comprises a mixed oxide of lithium and at least one metal selected from Ni, Co, Mn, Al.

8. The battery electrode is an anode (negative electrode), the total amount of the active material is at least 95% by weight of the total amount of the electrode powder mixture, and graphite and / or SiO ｘ The method according to any one of claims 1 to 7, comprising:

9. The method according to any one of claims 1 to 8, wherein no solvent is added to the electrode powder mixture.

10. 10. The method according to claim 1, wherein the electrode powder mixture has a percentile D90 of the particle size distribution of less than 500 μm.

11. 11. The method according to claim 1, wherein homogenization of the active material and the binder material and optionally the conductive additive is carried out in separate processes prior to the powder pre-treatment of the powder mixture.

12. The method according to any one of claims 1 to 11, wherein the electrode powder mixture is used for a lithium-ion battery electrode.

13. The method comprises the following steps: - transporting the resulting powdery and flowable electrode powder mixture by overflow and / or pouring through an outlet opening into the calendar assembly device and / or into the calendar gap, i.e. the gap between two counter-rotating rolls; - forming the electrode powder mixture in the calender as a roll-supported film; and - transferring the roll-supported film onto a current collector foil in a central calender gap and compressing the roll-supported film on the current collector foil in a rolling device into a battery electrode having a desired target thickness; The method according to any one of claims 1 to 12, comprising:

14. The method of claim 13, wherein the calender has at least four rolls.

15. The method comprises the following steps: - transporting the resulting powdery and flowable electrode powder mixture by overflow and / or pouring through an outlet opening into the calendar assembly device and / or into the calendar gap, i.e. the gap between two counter-rotating rolls; - forming the electrode powder mixture into a free-standing film in the calender; and - calendering the free-standing film in another calender stage to reduce film thickness and increase film density; and - transferring the free-standing film onto a current collector foil and compressing the free-standing film on the current collector foil in the central calendar gap or another calendar gap into a battery electrode having a desired target thickness; The method according to any one of claims 1 to 12, comprising:

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